A combustible sensor over-range alarm indicates a potentially explosive atmosphere. Failure to leave the area immediately may result in serious injury or death. In the event of an LEL over-range alarm, the IQ Force must be turned off, brought to an area that is known to be safe (containing 20.9% oxygen, 0% LEL, and 0 ppm toxic gases, and then turned on again to reset the alarm. The instrument must then be recalibrated before being put back in service. 2.5.7 LEL failure due to lack of oxygen alarm The LEL sensor in the IQ Force requires a certain amount of oxygen to function properly. When oxygen levels fall below 10.0% by volume, the IQ Force will show “---” in place of the LEL reading and display O, too and Loin successive screens in the location typically used for the LEL reading.